ci: Prune dangling images (NVIDIA-NeMo#11885)

Signed-off-by: oliver könig <okoenig@nvidia.com>
Signed-off-by: Youngeun Kwon <youngeunk@nvidia.com>

Author: ko3n1g

.github/workflows/_test_template.yml

@@ -47,7 +47,7 @@ jobs:
     steps:
         - name: Docker system cleanup
           run: |
-            docker system prune -a --filter "until=24h" --force || true
+            docker system prune -af --filter "until=24h" --force || true
 
         - name: Docker pull image
           run: |